From 0cce43a716b40c555892b1d22b41d390ef524ec8 Mon Sep 17 00:00:00 2001 From: David Rowley Date: Wed, 3 Jul 2019 23:45:25 +1200 Subject: [PATCH] Don't remove surplus columns from GROUP BY for inheritance parents d4c3a156c added code to remove columns that were not part of a table's PRIMARY KEY constraint from the GROUP BY clause when all the primary key columns were present in the group by. This is fine to do since we know that there will only be one row per group coming from this relation. However, the logic failed to consider inheritance parent relations. These can have child relations without a primary key, but even if they did, they could duplicate one of the parent's rows or one from another child relation. In this case, those additional GROUP BY columns are required. Fix this by disabling the optimization for inheritance parent tables. In v11 and beyond, partitioned tables are fine since partitions cannot overlap and before v11 partitioned tables could not have a primary key. Reported-by: Manuel Rigger Discussion: http://postgr.es/m/CA+u7OA7VLKf_vEr6kLF3MnWSA9LToJYncgpNX2tQ-oWzYCBQAw@mail.gmail.com Backpatch-through: 9.6 --- src/backend/optimizer/plan/planner.c | 8 +++++ src/test/regress/expected/aggregates.out | 45 +++++++++++++++++++++++- src/test/regress/sql/aggregates.sql | 24 ++++++++++++- 3 files changed, 75 insertions(+), 2 deletions(-) diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index eadc04222e..401299e542 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -3124,6 +3124,14 @@ remove_useless_groupby_columns(PlannerInfo *root) if (rte->rtekind != RTE_RELATION) continue; + /* + * We must skip inheritance parent tables as some of the child rels + * may cause duplicate rows. This cannot happen with partitioned + * tables, however. + */ + if (rte->inh && rte->relkind != RELKIND_PARTITIONED_TABLE) + continue; + /* Nothing to do unless this rel has multiple Vars in GROUP BY */ relattnos = groupbyattnos[relid]; if (bms_membership(relattnos) != BMS_MULTIPLE) diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out index 2e5ce8cc32..ef8eec3fbf 100644 --- a/src/test/regress/expected/aggregates.out +++ b/src/test/regress/expected/aggregates.out @@ -1147,9 +1147,52 @@ explain (costs off) select * from t3 group by a,b,c; -> Seq Scan on t3 (3 rows) -drop table t1; +create temp table t1c () inherits (t1); +-- Ensure we don't remove any columns when t1 has a child table +explain (costs off) select * from t1 group by a,b,c,d; + QUERY PLAN +------------------------------------- + HashAggregate + Group Key: t1.a, t1.b, t1.c, t1.d + -> Append + -> Seq Scan on t1 + -> Seq Scan on t1c +(5 rows) + +-- Okay to remove columns if we're only querying the parent. +explain (costs off) select * from only t1 group by a,b,c,d; + QUERY PLAN +---------------------- + HashAggregate + Group Key: a, b + -> Seq Scan on t1 +(3 rows) + +create temp table p_t1 ( + a int, + b int, + c int, + d int, + primary key(a,b) +) partition by list(a); +create temp table p_t1_1 partition of p_t1 for values in(1); +create temp table p_t1_2 partition of p_t1 for values in(2); +-- Ensure we can remove non-PK columns for partitioned tables. +explain (costs off) select * from p_t1 group by a,b,c,d; + QUERY PLAN +--------------------------------- + HashAggregate + Group Key: p_t1_1.a, p_t1_1.b + -> Append + -> Seq Scan on p_t1_1 + -> Seq Scan on p_t1_2 +(5 rows) + +drop table t1 cascade; +NOTICE: drop cascades to table t1c drop table t2; drop table t3; +drop table p_t1; -- -- Test combinations of DISTINCT and/or ORDER BY -- diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql index ca0d5e66b2..17fb256aec 100644 --- a/src/test/regress/sql/aggregates.sql +++ b/src/test/regress/sql/aggregates.sql @@ -406,9 +406,31 @@ group by t1.a,t1.b,t1.c,t1.d,t2.x,t2.z; -- Cannot optimize when PK is deferrable explain (costs off) select * from t3 group by a,b,c; -drop table t1; +create temp table t1c () inherits (t1); + +-- Ensure we don't remove any columns when t1 has a child table +explain (costs off) select * from t1 group by a,b,c,d; + +-- Okay to remove columns if we're only querying the parent. +explain (costs off) select * from only t1 group by a,b,c,d; + +create temp table p_t1 ( + a int, + b int, + c int, + d int, + primary key(a,b) +) partition by list(a); +create temp table p_t1_1 partition of p_t1 for values in(1); +create temp table p_t1_2 partition of p_t1 for values in(2); + +-- Ensure we can remove non-PK columns for partitioned tables. +explain (costs off) select * from p_t1 group by a,b,c,d; + +drop table t1 cascade; drop table t2; drop table t3; +drop table p_t1; -- -- Test combinations of DISTINCT and/or ORDER BY -- 2.40.0